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Worms in Chickens


By Dr Rob Marshall


There are many worm parasites that infect poultry. The best way to manage them is to administer worm treatments on a routine basis and to provide conditions that help to encourage your birds to develop a natural resistance against them.

The most common worms of poultry are roundworms, tapeworms, hairworms and caecal worms. All of these worms affect the health of chickens in a significant way and most importantly predispose them to many other problems.

Chickens may die when round worms mature simultaneously and obstruct the intestines. These fatal sudden onset type infections are most likely to occur when wet spells follow drought.

Tapeworms are unlikely to cause such dramatic losses although they may also obstruct the intestines. There main effect is to cause malnutrition and render infected birds susceptible to other infectious agents.

The overall health of chicken flocks can be improved simply by administering worm treatments from a young age as part of a regular routine. Some worms treatments (e.g. levamisole) are highly recommended for young chickens as they also stimulate natural immunity. Others (e.g. ivermectin or moxidectin) have dual functions and kill lice and mites as well as worms.

Many worms require intermediate hosts such as snails, slugs, cockroaches, grasshoppers, weevils, ants and other insects in order to infect chickens. These worms are common in show and backyard poultry and recurring infections are likely when measures are not taken to control these intermediate hosts.

Other worms infect chickens directly from the soil or garden where the worm eggs are able to survive for many years. Because it is not possible to kill the worm eggs in the soil, the control of these worms relies upon regular worm treatments and good nutrition for the young chickens in order for them to develop a natural resistance as adults.

Research has shown that chickens develop a greater immunity to worms when they are older than 3 months of age and also receive diets high in vitamins A and B, as well as good levels of calcium and lysine. For this reason it is good sense to adopt a health programme that uses nutritional supplements to enhance natural immunity and help prevent worm infections in a natural way.


Recommended Worm Treatments


  • All wormer tablet

    - Prazole (1 tablet per 500gram body weight)
    - Levamisole (98%w/v) (1 teaspoon per 5 litres of drinking water).


  • Moxidectin and Praziquantel

    - GTWormer (5mls/2 litres of drinking water for 2 days). This is a combination tapeworm, general worm and lice treatment.


Symptoms for Worm Infections


Worm outbreaks may occur following prolonged wet periods during the warmer months of the year. Young chickens are most affected by these outbreaks but adult birds may also show signs of illness.

Worm outbreaks are often associated with increased insect, snails, slug and earthworm activity, so that a preventative worm treatment is often helpful when these creatures are seen in increasing numbers.

Roundworms, hairworms and caecal worms are spread directly from a contaminated poultry house environment or backyard soil where their eggs may survive for many years waiting for the right conditions of warm wet conditions to become infectious. For this reason worms are less of a problem during drought periods but become a major problem following drought-breaking rains. This situation has arisen for many poultry flocks over the past two years.

Although symptoms vary according to the type of worm infection, there are common signs that warrant a decision to worm out the birds. These include changes in flock behaviour where young chickens are seen to huddle together, gather around the food or water containers. A normally tame flock may suddenly become skittish and fearful of human contact.

Symptoms in adult birds include the sudden onset of a pale or bluish colour to the comb, diarrhea and smelly droppings, blood or bubbles in the droppings, a pasted vent, prominent keel bone, death of several young birds with the above signs.


Worm Treatment Trial


A treatment trial using Levamisole (Prazole tablets by mouth or levamisole in the drinking water) is recommended when worms are suspected or any of the above symptoms appear in a flock.

The true health of the flock can also be assessed by the response of the individual chicken or flock to the levamisole treatment. A positive response (i.e. the birds suddenly look very well again within two days of treatment) indicates the symptoms are the result of any worm type except tapeworms. There will also be a positive effect with many minor ailments because levamisole has the ability to stimulate immunity and kick start recovery of this type of sickness. Most importantly there will be a negative response (i.e. some birds will become obviously sick) when a serious underlying disease process is present. A negative response allows the breeder to prevent unnecessary losses by seeking veterinary help during the early stages of a disease rather than later.

A worm problem is present when there is a rapid positive response to this treatment. When this occurs then a follow up treatment with a product that also treats tapeworms (Prazole tablets or GT wormer) is recommended one week later.


Diagnosis of Worms


A microscopic examination of the droppings looks for worm eggs. This type of examination is used to identify which worms are present and often there is more than one worm type present. A microscopic examination of fresh droppings may miss tapeworms which release segments rather than eggs or early stage infections when the worms are still immature and yet to produce eggs.

Self-diagnosis is another option for breeders, who may perform post mortem on dead birds and look for the presence of worms. During a postmortem examination the diagnosis of worms is straight forward as they can often be seen with the naked eye. It is important to examine the crop, stomach, gizzard intestine and caecum in order to identify the different worm types. Below is a physical description of the common worm types of chickens.




Roundworms are easy to recognize because they look like spaghetti and are found in the small intestines. They are often found in high numbers and cause death by blocking the intestines with their mass. A Piperazine worm treatment rather than Levamisole treatment is required when roundworms have been found to obstruct the bowel. Levamisole kills the worms outright and the dead worms often obstruct the bowel causing death a few days after this worm treatment. Instead Piperazine is a worm medicine that paralyses and slowly kills roundworms and allows the worms to unravel before being purged from the bowel.

Levamisole is then used following the treatment with piperazine. Repeat worm treatments are then given each fortnight for three treatments. Three monthly follow up treatments are then introduced as part of an ongoing prevention routine.




A high percentage of chickens may be infected with tapeworms if they are reared on range or in backyard flocks. These parasites are found more frequently during warmer seasons when intermediate hosts are abundant. Tapeworms may obstruct the intestine of an infected bird in the same way as roundworms. Tapeworms are more ribbon like and clump together in a tangled mass of thin strands whereas roundworms are more spaghetti like in appearance.

Worm treatments containing praziquantel are used to kill tapeworms. Two follow up treatments at 3 week intervals are then recommended. Routine three monthly seasonal treatments together with control measures against flies, beetles, slugs, snails, earthworm ingestion is necessary to prevent further infection.

Tapeworm problems are more widespread when insect activity peaks during the warm spring, summer and autumn months. Insect control is a necessary part of tapeworm treatments if recurrent outbreaks are to be avoided.


Blood Sucking Worms


These worms are often found in the crop and stomach. They appear as small hair-like worms or bright red worms in the stomach. Common symptoms are ill thrift, pale combs from anemia and blood in droppings. Chickens eating cockroaches, snails, earthworms and slugs are prone to blood sucking worms. These creatures must also be controlled in order to prevent further infection.


Caecal Worms


These are small 1cm long white worms found in the caecum. They are associated with chickens eating earthworms and are also involved with blackhead in peafowl. Levamisole is the treatment of choice together with preventing the chickens from eating earthworms.


Eye Worms


This worm is associated with eye symptoms such as eye rubbing and infected eyes. Cockroaches are involved in its transmission to chickens. Moxidectin treatment is the best treatment.


Worm Prevention - Routine Treatments


Infection with worms has a profoundly negative effect on the ongoing health of chickens, so much so that I strongly believe prevention is the best cure for worms. Ask your veterinarian for the best worm treatment option for your flock.


Young Chickens


Good nutrition and routine treatments against worms administered each month from one month until six months of age will help young birds develop into strong adults with a natural ability to repel worms even when they are exposed to an environment contaminated with worm eggs. See Poultry Health Programme.

Worm treatments may be administered by the drinking water or directly by mouth using tablets. It is important to keep the same age groups together until 6 months of age in order to limit the opportunity of the worm parasites to prosper. In addition it is important not to mix young chickens with other poultry species such as turkeys, pheasants, ducks or peafowl in order to prevent other more serious diseases associated with worms.


Recommended young chicken worm routine:


Monthly worm treatments until 6 months of age are beneficial to the long-term health of young chickens.

  • 1 month old - Levamisole treatment


  • 2 months old - GTWormer

  • 3 months old - Levamisole treatment

  • 4 months old - GTWormer

  • 5 months old - Levamisole treatment

  • 6 months old - GTWormer

This first levamisole treatment is very important as the response of the young chickens to this treatment is used to reveal their true health. Healthy youngsters will respond in a very positive manner to this initial treatment and become more alert, active, inquisitive, tame and develop a tight brighter plumage within two days of the treatment. Young chickens harbouring a health problem will fluff up and become less interested in eating following the levamisole treatment.

A levamisole treatment helps determine the true health of your young chickens and encourages you to seek veterinary help if the birds fail to show a positive response.

Levamisole is the most important worm treatment, as it will kill all worms except tapeworm. It has a most important added effect of stimulating the natural ability of your young chickens to repel all disease.


Adult Chickens


Adult chickens do not require as frequent worm treatments as the young chickens. Instead they should receive strategic treatments at times when worm infection is most likely to occur. Worm treatments are recommended each 3 months at the beginning of spring, summer and autumn when warm wet conditions favour worm infections in adult chickens. Many of the worms that infect adult chickens require an intermediate host before they are able to infect them. A large part of worm prevention involves the control of these creatures that include cockroaches, beetles, houseflies, slugs and snails. Cleaning away any uneaten table treats each evening and applying insecticides to the surfaces of pens are a recommended routine used to help prevent these type of worm problems.


Recommended adult chicken worm routine:


  • Beginning spring - Levamisole or Prazole treatment


  • Beginning summer - GTWormer

  • Beginning autumn - Levamisole or Prazole treatment


Withholding Period


There is a 7-day long withholding period following the administration of worm treatments. For those with back yard chickens I suggest you boil the eggs and feed them back to the chickens during this period of time. The benefit for the chickens following the worm treatment far outweighs the inconvenience of not having perfectly fresh eggs.


Chinese Silkies are our first choice backyard chicken. They are robust, loveable, quiet, lay good quality eggs and make ideal pets.

Our programmes are a simple and effective way to provide your chicken companions with the best possible care.

Click for information regarding our holistic methods for managing chicken diseases.

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